1. Field of the Invention
The present invention relates to a parking brake actuation system for a motor vehicle and, more particularly, to an improved electrically driven parking brake actuation assembly that can be electrically or manually released.
2. Description of Related Art
Some automobiles or other motor vehicles are equipped with power-assisted parking brakes. A power-assisted parking brake is an electrically driven brake actuation system that allows remote actuation of the brakes of the automobile (typically only the rear brakes) to prevent movement of the automobile when parked. These systems include an electric motor and a rotational-to-linear drive mechanism for translating the rotational movement and torque of the motor to linear displacement of a brake cable mechanically connected to the brakes. Upon remote actuation, the motor rotates to effect displacement of the brake cable to set the brakes. The brakes may similarly be remotely released by effecting reverse rotation of the motor. Additionally, the brakes may be manually released with a manual override in case of automobile power failure, to allow the automobile to be moved (e.g., towed). There are several disadvantages with brake actuation systems of current design.
The manual overrides usually do not allow unrestricted movement of the brake cable and brakes back to their home (unactuated) positions. This is due to the resistance to movement inherent within the brake actuation system itself, such as in the drive mechanism and the motor. Accordingly, use of the manual override does not necessarily ensure complete release of the brakes. Forced movement of the automobile with only partially released brakes can cause wear and/or damage to the brakes.
Additionally, in order to maintain actuation of the brakes, with some systems the motor must be continuously energized to maintain a holding torque on the drive mechanism. This continuous use of the motor significantly limits the useable life of the motor and therefore the brake actuation system. Alternatively, a separate locking device may be used to allow the motor to be de-energized without allowing slippage of the brakes. However, this superfluous componentry significantly increases manufacturing costs of the brake actuation system. Moreover, addition of such a separate component increases the size of the brake actuation system and correspondingly reduces orientation and space management options available for installation of the brake actuation system into an automobile.
Furthermore, prior brake actuation systems have been integrated with componentry of the vehicles themselves and have not been readily available for add-on or retro-fitting to other vehicles.
A first aspect of the present invention provides a power-driven parking brake actuation assembly for actuating a vehicle brake system via a brake activation linkage including an electric motor and a first rotatable member operatively connected to the electric motor so as to enable the motor to rotate the first rotatable member in a brake applying rotational direction. The first rotatable member is normally prevented against rotation in a brake releasing rotational direction. A second rotatable member is rotatable relative to the first rotatable member and includes a brake linkage actuator connectable to the brake activation linkage and movable to actuate the same. A torsion clutch spring is disposed between the first and second rotatable members and is configured to contract upon initiation of rotation of the first rotatable member by the motor in the brake applying direction so as to couple the second rotatable member to the first rotatable member for affecting rotation of the second rotatable member in the brake applying direction for actuation of the brake activation linkage. The clutch spring is also configured to remain contracted as the actuated brake activation linkage applies a force to the second rotatable member in the brake releasing direction so as to keep the second rotatable member coupled to the first rotatable member. This enables the first rotatable member to prevent rotation of the second rotatable member in the brake releasing direction. A selectively actuable brake release mechanism is operatively connected to the clutch spring such that movement of the release member expands the clutch spring to de-couple the second rotatable member from the first member, thus enabling the second rotatable member to rotate in the brake releasing direction.
The release mechanism may be manually powered or electrically powered, preferably by a source separate from the vehicle""s conventional main battery system, so that it can be released in the event vehicle power is lost and the main battery system is drained.
Another aspect of the present invention provides a brake actuation assembly including an electric motor having an output shaft and a drive assembly coupled to the output shaft. The brake actuation assembly also includes a pivot structure coupled to the drive assembly so as to be pivotable by the electric motor via the drive assembly. The pivot structure has connecting structure thereon configured to couple with a brake actuating linkage. The drive assembly is configured to lock in a brake actuated position upon movement thereinto. A release structure is coupled to the drive assembly to release the drive assembly from the locked brake actuated position. The release structure includes a pair of connecting portions positioned thereon at respective relative positions. Each of the connecting portions is configured to connect to a release cable assembly, such that the brake actuating assembly is capable of being disposed in two different installation orientations corresponding to the positions of the connecting portions.